Regeneron Pharmaceuticals, Inc. (NASDAQ: REGN) today announced that it received from Sanofi (NYSE: SNY) a notification under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (HSR Act) that Sanofi intends to acquire Common Stock of Regeneron through open market purchases and direct purchases from shareholders. As a result, Sanofi intends that the value of its ownership of voting securities of Regeneron stock will be in excess of the $500 million HSR Act notification threshhold.

Pursuant to the Investor Agreement between Regeneron and Sanofi dated as of December 20, 2007, as amended, Sanofi is bound by certain "standstill" provisions including an agreement not to acquire more than 30% of the outstanding shares of Regeneron's class A stock and common stock. Unless otherwise terminated pursuant to the Investor Agreement, these standstill provisions are in effect until the later of the fifth anniversaries of the expiration or earlier termination of the License and Collaboration Agreement, dated as of November 28, 2007, as amended, between Regeneron and Sanofi, and Regeneron's Collaboration Agreement dated as of September 5, 2003, as amended, with Aventis Pharmaceuticals Inc. (Sanofi's predecessor) for the development and commercialization of ZALTRAP® (ziv-aflibercept).